In processing an instruction sequence it is often necessary to branch off from the execution of a particular instruction sequence to an instruction at a location which is displaced from the location of a current instruction. The location that is branched to may be referred to as a "branch target" or a "target location." Such a process is often referred to as "branch" or sometimes a "wide branch" instruction and requires a certain number of processor operating cycles for its performance. Such an instruction might be contrasted with a "jump" instruction which requires a jump to any location not necessarily a location relatively closely displaced from the location of a current instruction.
The difference between a branch and a jump can be understood in the context of the MV-Series of data processing systems as made and sold by Data General Corporation of Westboro, Mass., for example. As used in connection with such systems, a jump is normally thought of as being made from a current location in memory to substantially any other location in memory, while a branch is normally thought of as being limited to one made from a current location as designated in a program counter (PC) to a location which is within a specified number of locations from such current location, e.g., to a location within a range from PC +127 to PC -128.
Since it is desirable generally to accelerate the processing of instructions in a digital computer or data processing system, it is helpful to devise techniques for reducing the number of operating cycles required to perform selected processing operations. One such operation which can be so accelerated is such a wide branch instruction operation.